Process for recovering cassiterite from ores



Jan. 26, 1965 J. B. DUKE PROCESS FOR RECOVERING CASSITERITE FROM ORES Filed March 20, 1962 C AMINE 8 C 2 FATTY ACID COLLECTOR REAGENTS GANGUE TAILINGS (SANDS &

TIN ORE MILL HEADS CRUSHING a GRINDING SCREENING SLIMES) TAILINGS CASSITERITE a GANGUE MACHINE DISCHARGE CONDITIONING FROTH FLOTATION GRAVITY TABLING CONCENTRATE WATER ROUGH GRAVITY TABLING moouu :r CLEANER CONCENTRATE GRINDING XANTHATE FLOTATION REAGENTS CONDITIONING SULIDE FROTH CASSITERITE RICH FROTH CONCENTRATE INVENTOR.

JAMES B. DUKE ATTORNEY States This invention relates to a process for recovering cassiterite from ores and relates especially to the concentration of cassiterite (SnO from oxidized minerals by froth flotation.

Tin is obtained from ores, such as those found in Bolivia, which contain a great variety of minerals. From a metallurgical point of view the ores consist essentially of quartz, tourmaline, feldspar, mica, iron oxides, a variety of sulfides (of which iron sulfide predominates) and small amounts of cassiterite which constitute the only valuable mineral in the ore. A typical Bolivian ore may contain about /2 to 2% cassiterite, 25 to 40% of pyrite, pyrrhotite and marcasite, 20% of siderite, to 20% of quartz, 15 to 20% sericite and 3 to 5% fluorite. At present these ores are concentrated by a gravimetric process, such as the procedure described in an article by O. M. Davila in Engineering and Mining Journal, vol. 158, No. 11, pages 100-108, entitled How Empresa Minera de Catavi Concentrates Tin Ores. The process involves a heavy media concentration in which the tin ore is crushed, jigged and tabled to produce a cassiterite concentrate which is subjected to froth flotation with a xanthate collector reagent to float sulfides from the cassiterite. By this procedure, a material assaying about 55% Sn is obtained. The recovery of cassiterite is reported to be at best only 55 to 60% as a result of losses in the gravimetric concentration steps.

Many attempts have been made to float cassiterite and a variety of collector reagents has been suggested, among which may be mentioned certain quaternary ammonium compounds, alkyl cetyl sulfate, oleic acid and sodium oleate. The results, however, have not been sufiiciently satisfactory because of the failure to develop reagents of adequate selectively for the cassiterite. As far as is known, cassiterite is not floated commercially.

After extensive experiments with a wide variety of reagents, a reagent which surprisingly exhibits exceptional selectivity for cassiterite has been discovered. This discovery has led to a simple economical process for recovering from tin ores a high grade cassiterite concentrate at an excellent weight recovery. The process, described hereafter, can obviate the sink float step previously containing 12 carbon atoms, e.g., laurylamine acetate. In

accordance with a preferred form of the invention, a specific anionic-active reagent, namely, lauric acid, is employed as a cooperative flotation collector reagent with the C amine. Preferably, the pulp is conditioned with fluoride ion before incorporating the collector reagent or reagents. The conditioned pulp is subiected to froth flotation to produce a cassiterite rich froth, leaving a substantial part of the gangue minerals in the railings.

The particular cationic reagent employed in carrying out this invention has been found to have excellent selectivity for cassiterite. Amines derived from fatty acids containing a greater number of carbon atoms than lauric acid, such as the primary amine of tall oil fatty acids, do not possess the selectivity of the C amine employed in carrying out this invention. The selectivity of laurylamine for cassiterite is improved significantly by the use of the cooperative lauric acid reagent. However, the latter is not an effective cassiterite collector reagent when employed in the absence of the amine.

The selection of lauric acid as the cooperative anionic collector reagent is an essential feature of this invention. Substitution of other familiar oxide collector reagents or cooperative reagents, such as oleic acid or fuel oil, for the lauric acid cooperative collector reagent will give results markedly inferior to those obtained with lauric acid as the cooperative reagent. In fact, the substitution of various oils or even oleic acid for the lauric acid cooperative collector reagent may actually impair the selectivity of the cationic collector reagent. This result is surprising and unexpected since fatty acids, such as oleic acid and tall oil fatty acids, which have longer hydrocarbon chains than lauric acid employed in carrying out a preferred form of this invention, are widely used as collectors for metal oxide minerals while lauric acid is only rarely employed for collecting metal oxide minerals.

Lode tin ores, in addition to oxidized minerals, contain sulfide minerals (such as cylindrite, stannite, marmatite, pyrite, marcasite, pyrrhotite, antimonite, bismuthinite, sphalerite, galena, silver sulfides, franckeite and chalcopyrite). In beneficiating such ores, the mill feed, previously tabled if the nature of the ore indicates such pretreatment, is subjected to a sulfide flotation with a xanthate collector and the machine discharge product of the sulfide flotation is reagentized with the C amine (and preferably C fatty acid) and then floated to obtain a cassiterite rich concentrate. By this procedure, a 79% weight recovery of about 53% Sn0 grade has been obtained from a Bolivian tin ore assaying only about 1.23% SnO This invention will be more fully understood by the following description taken in conjunction with the accompanying drawing which is a flow sheet of a typical plant for concentrating cassiterite from a complex ore containing sulfide, quartz and silicate gangue minerals, in accordance with this invention.

As indicated in the flow sheet, the mill heads are crushed and ground to about 20 or 28 mesh, and preferably deslimed to remove primary and secondary slimes. The material is then gravity tabled, as by a Wilfley shaking table, to produce a rougher concentrate (heavies) and a tailing. The rougher concentrate can be retabled to produce a cleaner concentrate and a middling.

The cleaner concentrate is crushed, as to pass a 48 mesh or a 65 mesh screen and then deslimed. The deslimed feed is subjected to a sulfide flotation, as with the usual xanthate collector reagents. Present results indicate that it may be highly advantageous to incorporate fluoride ion into the pulp before reagentizing the pulp with xanthate and carry out sulfide flotation in an acid circuit. About 1 to 10 pounds of hydrofluoric acid per ton of dry feed can be used. Any of the usual xanthate collectors can be employed as the selective sulfide collector, as examples of which can be mentioned potassium ethyl xanthate, potassium n-butyl xanthate, potassium sec-butyl Xanthate, potassium amyl xanthate, potassium n-hexyl xanthate, sodium ethyl xanthate, sodium isopropyl xanthate and sodium sec-butyl xanthate. About /2 to 3 pounds of xanthate collector is used per ton of dry feed. The details of the sulfide flotation step will obviously vary with the nature of the sulfide minerals present in the tin ore and can be readily determined by applying the usual considerations 3 which are familiar to those skilled in the art. The conditioned pulp is aerated in any suitable flotation machine, removing a sulfide float and a tailing which is a concentrate of cassiterite together with oxidized minerals.

The machine discharge product of the sulfide flotation step is deslimed, as by decantation, and conditioned for froth flotation to recover a cassiterite rich concentrate. Fluoride ion, in the form of hydrofluoric acid, for example, is employed in amount of about 1 to 10#/ ton feed and is added before the cationic collector reagent or cooperative cationic and anionic reagents. The cationic C amine collector reagent is incorporated into the pulp in soluble form, such as the acetate or chloride salt. The quantity of C amine employed in carrying out this invention is about /2 to 2#/ ton (and preferably about 1#/ ton) of dry feed. Laurie acid cooperative reagent is employed in amount of about /2 to Sit/ton, preferably about 1 to 2#/ton. When employed in excess of about 2-#/ ton the cooperative anionic reagent tends to lose its effectiveness. The conditioning agents can be incorporated by stage addition.

The feed to the cassiterite flotation, usually after suitable dilution, is conditioned and subjected to froth flotation, withdrawing a froth product which is a concentrate of cassiterite. The froth may be cleaned one or more times to improve the grade. Recovery of cassiterite can be improved by recirculating middlings. The tailings of 7 the cassiterite flotation consist for the most part of quartz and silicate minerals.

While this invention has been disclosed with reference to its utility in concentrating the mineral cassiterite from deslimed flotation feed, it will be understood that it is also fully within the scope of this invention to employ the selective cassiterite collector reagent or reagents in concentrating cassiterite in slimed pulps by the flotation procedure described in US. 2,990,958.

EXAMPLE I The following example illustrates the concentration of cassiterite from the ore operations of Empresa Minera de Catavi in Bolivia. The ore assayed 1.23% Sn, principally as cassiterite, representing 1.56% SnO The ore also contained cylindrite Pb Sb SnSn, stannite (Cu SFeSSnS pyrite, marcasite, pyrrhotite, antimonite, bismulthinite, sphalerite, galena, silver sulfides, franckeite, chalcopyrite, quartz, tournmaline, limonite, hematite, feldspar, sericite, mica, topaz and fluorite.

T abling Percent Percent Percent Sn Sn Dis- Cassitcrtribution ite (SnOr) Percent Products Wt.

1.24 100. (L23) 100.0 1. 57 14. 7 2 s. 53 77. 4 8.29 37.7 7 0.27 s. 1 0.34 Table tails 47. 6 30.37 14. s 0. 47 Table tails +325 mesh 29.2 fit 5.0 0. 30 Table tails 325 mesh 18. 4 2 0. 8.9 0.77

1 Calculated. 2 Assayed.

Sulfide float The minus 20 mesh table concentrate containing 8.29% cassiterite, representing 77.4% by weight of the cassiterite in the mill heads, was crushed to pass a 65 mesh screen. After settling, water was decanted from the crushed ore and the minus 65 mesh feed was put into a gm. Minerals Separation Sub A flotation machine, diluted to about 10% solids with water acidified with sulfuric acid to a pH of 3. 'The pulp was conditioned for 3 minutes with the following reagents.

Reagent Quantity, ton dry feed Hydrofiuoric acid 10.0 Sulfuric acid 5.0 Potassium sec-amyl xanthate 2.0 Pine oil 0.36

the pulp was aerated and a froth product removed for 2 minutes, removing a sulfide froth product. The residue in the flotation machine was conditioned for 1 minute with 1#/ton of sec-amyl xanthate and a second froth product withdrawn for 1 minute. The combined sulfide machine discharge products were deslimed by decantation and pulped back into the flotation machine.

Cassiterite float The deslimed sulfide machine discharge product was conditioned for 1 minute with the following reagents in the order given:

Reagent Reagent quantity, ton dry feed Hydrofluoric acid 5.0 Laurylamine acetate (Armac 12.) 1.0 Laurie acid (Neofat 265) 1.2

The conditioned pulp was frothed for 2 minutes, removing a cassiterite froth product and a tailing. The froth product was refloated two times without addition of reagents.

Following are the metallurgical results of the sulfiide and cassiterite flotation operations and of the combined tabling and flotation operations.

FLO'IATION METALLURGICAL RESULTS Percent Percent Percent Percent Products Wt. Sn Sn Dis- Oassltertributlon lte Feed 100.0 6. 53 1 Sulfide FJ? 17. 2 1. 63 -ff? Sulfide M.D. sllme Tin cone--- Tin mid-L 7. Tin mid- 2. Tin tail 56.

TABLING AND PLOTATION METALLURGICAL RESULTS Percent Percent Percent Percent Products Wt. Sn Sn Distcassitertribution ite (S1103) Feed 100.0 1. 23 100.0 1. 56 T n flotn. conc 1.8 41. 16 60.3 52.26 Tm flotn. waste. 12. 9 2. 40 25.2 3.05 Table mid and tall 85.3 0. 21 14. 5 0. 27 Total waste 98. 2 0. 50 39. 8 0163 EXAMPLE II To illustrate the desirability of using a C fatty acid with a C amine, the procedure of Example I was repeated in full with the exception that in the cassiterite flotation step no fatty acid or other oiling reagent was employed with the C amine. A 77% recovery of cassiterite of 50.0% grade was obtained.

EXAMELE III In this example, the mill feed was prepared in the same way as in Example I. The feed was then conditioned for sulfide flotation in the same manner as in Example I, using the same reagents. The machine discharge product was deslimed and conditioned for cassiterite notation in the same manner as in Example I and with the same reagents with the exception that 1.2 pounds of red oil (oleic acid) was substituted for the 1.2 pounds of lauric acid employed in Example I. The pulp was aerated and a froth product removed for 2 minutes as in Example I.

The cassiterite content of the tin concentrate was found to be only 42.8% at a 72% weight recovery. This result, obtained using oleic acid as the anionic reagent with the C amine, was poor as compared with the results obtained using lauric acid with the C amine (Example I) Where a 78.9% recovery of 52.26% grade was obtained. This result was also poorer than that obtained using the C amine without any cooperative collector reagent where a 77% recovery of 50.0% grade was obtained.

When 5.0 pounds of fuel oil was substituted for the lauric acid of Example I, the Sn analysis of the tin concentrate was only 37.2%. Therefore the fuel oil was not a suitable cooperative collector reagent.

I claim:

1. In a method for concentrating cassiterite from oxidized gangue, the steps which comprise:

forming an aqueous pulp containing cassiterite and oxidized gangue minerals,

conditioning said pulp for froth flotation with a Water-soluble salt of laurylamine as a collector reagent and lauric acid as a cooperative collector reagent,

and subjecting the pulp thus conditioned to froth flotation in an acid circuit, thereby forming a froth product which is a concentrate of cassiterite in the pulp.

2. In a method for concentrating cassiterite from oxidized gangue, the steps which comprise:

forming an aqueous pulp containing cassiterite and oxidized gangue minerals,

conditioning said pulp for froth flotation with fluoride ion,

laurylamine acetate as a collector reagent and lauric acid cooperative collector reagent,

and subjecting the pulp thus conditioned to froth flotation in an acid circuit, thereby forming a froth product which is a concentrate of cassiterite in the pulp.

3. In a method for concentrating cassiterite from oxidized gangue, the steps which comprise:

forming an aqueous pulp containing cassit-erite and oxidized gangue minerals,

conditioning said pulp for froth flotation with fluoride ion,

a water-soluble salt of laurylarnine and lauric acid,

and subjecting the pulp thus conditioned to froth flotation in an acid circuit, thereby forming a froth product which is a concentrate of cassiterite in the puip.

4. In a method for concentrating cassiterite from a tin ore in which cassiterite is associated with sulfide and also oxidized gangue minerals including quartz and silicate minerals the steps which comprise:

forming an aqueous pulp of said ore,

conditioning said pulp for sulfide flotation with a Xanthate collector reagent, and subjecting the thus conditioned pulp to froth flotation, thereby producing a froth product which is a concentrate of sulfide minerals in said ore and a machine discharge product which is a concentrate of cassiterite and oxidized gangue minerals,

conditioning a pulp of said machine discharge product for froth flotation with a water-soluble salt of laurylamine and lauric acid as cooperative collector reagents, and subjecting the pulp thus conditioned to froth flotation in an acid circuit, thereby producing a froth product which is a concentrate of cassiterite in said pulp.

5. In a method for concentrating cassiterite from a tin ore in which cassiterite is associated with sulfide and also gangue minerals, including quartz and silicate minerals, the steps which comprise:

forming an aqueous pulp of said ore,

conditioning said pulp for sulfide flotation with a xantnate collector reagent, and subjecting the thus conditioned pulp to froth flotation, thereby producing a froth product which is a concentrate of sulfide minerals in said ore and a machine discharge product which is a concentrate of cassiterite and oxidized gangue minerals,

conditioning a pulp of said machine discharge product for froth flotation with a fluoride ion, laurylamine acetate and lauric acid, and subjecting the pulp thus conditioned to froth flotation in an acid circuit, thereby producing a froth product which is a concentrate of cassiterite in said pulp.

6. A method for concentrating cassiterite from a tin ore in which cassiterite is associated with sulfide and also oxidized gangue minerals which comprises:

tabling said ore, thereby producing a table concentrate which is richer in cassiterite and sulfide minerals than said ores and a table tailings which is largely composed of gangue minerals,

forming an aqueous pulp of the table concentrate,

conditioning said aqueous pulp for froth flotation with a collector reagent selective to sulfide minerals in the pulp, and subjecting the pulp to froth flotation, thereby producing a froth product which is a concentrate of sulfide minerals in said table concentrate and a machine discharge product which is a concentrate of cassiterite and oxidized gangue minerals in said table concentrate,

conditioning an aqueous pulp of said machine discharge product for froth flotation with hydrofluoric acid, laurylamine acetate and lauric acid as cooperative collector reagents, and subjecting the pulp thus conditioned to froth flotation in an acid circuit, thereby producing a froth product which is a concentrate of cassiterite.

7. The method of claim 6 in which sulfide flotation is carried out in an acid circuit.

References Cited in the file of this patent UNITED STATES PATENTS 2,000,350 Patek May 7, 1935 2,012,609 Lenher Aug. 27, 1935 2,267,307 Ralston and Pool Dec. 23, 1941 2,297,689 OMeara Oct. 6, 1942 2,381,662 Gaudin Aug. 7, 1945 FOREIGN PATENTS 122,177 Australia Sept. 19, 1946 OTHER REFERENCES Engineering and Mineral Journal, volume 158, number 11, pages 108 (Davila).

UNITE STTES PATENT @FFMIE QER'HEMATE 5'- Patent No, 3,163,502 January 26 1965 James B. Duke It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected belowa Column 3, line 45, for "bismulthinite" read bismuthinite 001mm 4, line 14, for "the" read The column 6 line 69 for "Mineral" read Mining Signed and sealed this 20th day of April 1965.

(SEAL) Aitest:

ERNEST W0 SWIDER EDWARD J. BRENNER Anesting Officer Commissioner of Patents 

1. IN A METHOD FOR CONCENTRATING CASSITERITE FROM OXIDIZED GANGUE, THE STEPS WHICH COMPRISE: FORMING AN AQUEOUS PULP CONTAINING CASSITERITE AND OXIDIZED GANGUE MINERALS, CONDITIONING SAID PULP FOR FROTH FLOTATION WITH A WATER-SOLUBLE SALT OF LAURYLAMINE AS A COLLECTOR REAGENT AND LAURIC ACID AS A COOPERATIVE COLLECTOR REAGENT, 